20 May, 2011

Less than a week working at VO and I already wanted to taste the 650b nectar. I have been riding larger tires for quite some time, but while touring the tires I ride weigh more than some modern racing frames and I have come to realize that at some point in tire size, bigger is not necessarily better. Having settled into town, I opted for a lighter, faster tire; something that would race around town a bit, then take me out to the country with greater ease and enjoyment. The list is short for quality, medium volume tires that would fit my 1985 Schwinn High Sierra or my girlfriend‘s Surly LHT; both are 26” bikes with drops and touring equipment. I saddled up on a pair of 38mm Panaracer T-Serv tires, and was immediately underwhelmed by the ride of small wheels and smaller tires.

The workshop at VO is full of treasures, and I found a pair of space-age cantilever brakes (the next version of the Grand Cru) that I wanted to test. Upon mounting them, I realized that they had a lot of vertical adjustment…some quick calculations and a few minutes later there was a 650b wheel mounted in my frame with the brakes adjusted at the top of their range. The thought of finally riding high-quality, larger volume tires seemed heaven-sent. Road bikes have many high quality tires to choose from, although they are mostly too narrow for my needs. My mountain bike frame is happy with many tough, long-wearing road touring/commuting tires, but the ride quality of even the best options is a bit uninspired. The magic of 650b, I realized was the option to ride lightweight, high-quality tires with reasonable air volume like the Pacenti Neo-Moto without undersized or oversized wheel dimensions. In short, I didn’t have to choose anymore-- I could ride nice, big tires. I mounted a pair of Pacenti Pari-Moto tires and was immediately hooked. The volume of the tire, the supple casing, and lightweight (less than 300g) made for the most lively ride I’ve ever experienced. With the 650b Pari-Moto, my wheel is the same size as my previous touring wheel, thus, the bike handled in a more familiar way than it did with the undersized Panaracer T-serv tires.

In an effort to deshroud the mystery of wheel/tire size, I calculated that the 26 x 1.75 (653mm…650!) wheel I had been riding had nearly the same nominal outside diameter as the most common 650b tire sizes (38/650b results in a 660mm wheel). I had been riding this wheel size all along, only the details of rim and tire size had changed. This approximate dimension is also shared by narrow high pressure road tires, whose outside dimension with 700c/23mm tires is 668mm.. The discussion of ideal wheel sizes is overstated I discovered, as they are all nearly the same. It is by selection of a tire size to suit your riding needs that a specific rim dimension becomes relevant.

If you wish to ride tires under 32mm, 700c works well as there as more than a few tires to choose from. For tires over 42mm, 26” is a good place to be. But if you want the dreamy, quick and comfortable ride on high quality, larger volume tires between 32-42mm, 650b is where it’s at.

26“ to 650b conversion details: Most classic mountain bikes and some popular modern offerings such as the Surly LHT (26”) have adequate clearance for all of the smooth tread 650b tires. A 650b/38mm wheel actually suits the dimensions of the LHT better than a narrow 26”/32-38mm wheel, which leaves gaping clearances and unfamiliar handling. Conversion simply relies on a brake with 12.5 mm of vertical adjustability (half the 25mm difference between 559 and 584). We have already identified that Tektro CR720 brakes work at the top of their range, as did a prototype Grand Cru brake hanging out in our shop. Of course there are a few v-brake designs that have been around since the 90’s with loads of vertical adjustment as well.

A little about Nicholas,

Since diving into bike touring three years ago, Lael and I have toured around much of the US, including trips on both coasts (three times on the west coast). Three months in France early last spring allowed us ample time to travel the countryside, from our home in St. Malo, Brittany to Chamonix-Mt. Blanc and back, among many shorter regional trips. This past winter we biked south from Seattle and down the Baja Peninsula, then sailed to the mainland and rode into the Sierra Madre to the Copper Canyon. We have lived and worked seasonally in St. Malo, FR, Denali, AK and finally in Key West, FL where we worked as pedicab drivers for several months to escape the northern winter.

36 comments:

Thank you for this post, answers many of the questions I've been harboring about exactly this conversion. While I'm okay with my current 26" setup, rim braking surfaces don't last forever (not even close to forever) with my year round commute. I've thought of converting to 650b next time I need wheels, I was just unsure of my bike's clearance and canti brake range. More posts like this please!

I've had similar thoughts on my 26" wheeled Long Haul Trucker, but never found too much evidence of it being worth the trouble. However, your article combined with some info found on the 650b list has me thinking it's worth a try with the 650b wheels I have on hand. The <56cm LHT frames really do look/feel odd with <1.5" wide 26" tires, on an unloaded bike at least. It's a bike that demands fat tires and heavy loads.

Thanks for this useful post. I have been scheming a 26 to 650b conversion for a vintage Stumpjumper. Planning to turn it into a nice commuter that's also capable on fire roads and dirt paths.It's nice to know that the Tektro cantis work on 650b. That was one thing that I was wondering about.

I like your interest in maintaining a consistent outside diameter. The best part is that I believe this is exactly what the A, B, C tire sizing was designed to do:650A (ISO 590mm) used narrow tires,650B (ISO 584mm) used medium tires, and 650C (ISO 571mm) used fat tires, all to achieve similar outside diameters.So it's ironic that 650C is now almost exclusively a super-skinny-tired tri-bike size. How did that happen?

Nice article, a couple more things to keep in mind is that mountain bike frames tend to be ovebuilt for road or touring use (especially in smaller sizes) changing the high volume knobbies for a smaller faster city tire will increase their speed, but the price will be a much harsher ride! Switching to a 650B will not only restore the rolling diameter, but also preserves the higher volume which negates some of the inherent harshness of the mountain bike frame. Putting the 650B on a LHT, seems a little like having your cake and eating it too! a very good option at least until the new Polyvalents are available!

Some five years ago now I converted my 1983 Stumpjumper Sport to 700x38 by cutting off the canti mounts and adding disc brake tabs. I have done a number of similar conversions since, and there is plenty of room in many bikes that were designed for 26" wheels and mountain bike tires. By the way, Paul Components Moto BMX cantilever brakes have enough adjustment to convert a 26" wheel frame to 650b or 700c.

I finished building my second frame a couple of months ago. I wanted to use 650b wheels and tires, but designed it to also run 700c if I wasn't happy with my 650b "experiment".

Well, in the month and a bit since I got the frame back from the painters, I've ridden my original frame, a 700c bike that I love the ride of, exactly once, and the 650b frame a couple of dozen times. I'm running Panaracer/Riv Fatty Rumpkin's, which roll fast and absorb crappy roads like nothing else. Love 'em. But they're a tough sell to cyclists who don't know 650b (i.e. hard core roadies)

The thing that is holding back 650b as a platform, IMO, is the lack of inexpensive rims in the size that would allow a person to build up a basic set of wheels for $150 or so just to try them out. I was fortunate to find a reasonably priced set of wheels built up around 584ERD Weinmann ZAC 19's; these would be a perfect rim for this purpose, as the going price seems to be under $25 each; however, they are next to impossible to find. The next least expensive set of rims is the VO offering, but they are twice the price.

The Guth: Nice ride. I have a big place in my heart for fat tire drop-bar bikes. Perfect for escaping into the mountains, especially in you neck of the woods.

Elsewhere on the net I have seen Tektro Oryx brakes happily mated to 650b rims. Good news for LHT owners with stock brakes.

Paul advertizes 60mm of vertical adjustment for the Moto BMX brake, which allows for 26" to 700c conversion, and everything in between. This may be the solution to those that are dedicated to owning one bike (and three wheel sets). Of course a proper v-brake lever would be necessary.

James: In my experience, 27" to 700c conversion does not require new brakes. Many 80's touring bike were specced with Dia-Compe cantilevers, many of which are actually the best solution. In addition, smooth post cantilever brake pads like those from Kool Stop have loads of pad material, thus allowing a little uneven pad wear if you cannot get the pad perfectly level. I estimate putting over 6000 miles on a pair of pads salmon Kool Stop pads. They are indefatigable.

Three Speed: Some red Hetres would really spice up that Hi-Ten touring machine. I would love the juxtaposition of a steel-body Shimano SIS derailleur backdropped by Hetre tires. Most importantly, does you bike plane?

Hi. I was wondering about other conversions. I have a bridgestone 200 mixte that will convert to 650b according to the guidelines posted here: http://www.bikeman.com/content/view/1161/33/ The bridgestone originally had 27" wheels. I noticed in a previous post Chris said he wasn't an advocate of 650b conversions. I'm wondering why he made this comment but I'm pretty sure it's just because there are details in bicycle geometry that work best with 650b wheels. I'm guessing that the fork rake ideally should be calculated to accommodate for the extra cushion of the wider tires. In your opinion which is best to convert to 650b? 27", 700c or 26" wheeled bicycles? Can you discuss some of the specifics of 650b frame geometry?

The outer edge of the tire diameter would be the same for the A B and C sizes, the larger rim having the smallest tire and the smallest rim having the largest tire. Possibly all intended to fit the same bike? You could have three wheel sets for each bike depending on what you were doing?

The A rim would be the largest diameter and would take a narrow tire (appx 1 1/4"-1 3/8"). Intended for the smoothest roads/paths.

The B rim would be a smaller diameter and would take a medium width tire (appx 1 1/2"). Intended for urban/cobblestone riding.

The C rim would be smallest (strongest) and would take a wide tire (appx 1 3/4"). Intended for racing.

Since the early (non-velodrome) races were on what would've been extremely rough, rutted, unpaved roads, you would need those small rims/wide tires. As road conditions improved over the 20th century, racers were able to get by with narrower tires. Tall road racers continued to use 700C rims, the shortest continued to use 650C. Instead of using wide tires, they downsized to a ridiculous sub 1" tire.

The 700a and 700b are long gone (until recently they were still possible to source from a few wholesalers, but I haven't seen any in a long time). Wide 700c (622) tires are back in 29"er form, but generally wider than 1 3/4.

700d (587) was a super short lived model, even smaller than 700c (putting it between 650a and 650b, but with a wider tire. Appeared on an 80's ATB, by Giant?

650a (590) is the 26x1 3/8 size common on many British 3 speeds. Intended for modern urban pavement.

650b (584) is the size on many randonneur/porteur bikes intended to be ridden on mixed road conditions.

650c (571) used on small road bikes with sub 1" tires and Schwinn heavy-weight bikes with 1 3/4" tires.

My 1985 Trek 720 didn't need new brakes when I converted it from 27" to 700c.

650Bs aren't for us tall guys: Larger frames (61cm+) that were built for 700s look comical with 650Bs mounted. If the appearance doesn't deter you, you will likely need new brakes,and you'll probably be scraping pedals, at least occasionally.

In my experience with frame design, I am far more on the side of wheel diameter corresponding with tire width. The effective difference between wheel diameters as demonstrated by this post is far too minuscule for any rider to notice a difference in the geometry. For conversions, I would agree it is important to consider bottom bracket drop. For most road frame that have clearance for 28s max, pedal strike is rarely an issue since bottom brackets are far too high these days. I've based all these points on my own 7OOc to 65Ob conversion; which is a 65cm c-t-c. I am also brazing a 68cm frame designed around Grand Bois Hetres. Though 7OOc has a wider array of tire choices, 65Ob presents a few very high quality tires worth the investment. Perhaps if Grand Bois or Challenge made a 7OOc tire over 32mm wide, I'd revisit the possibility, but I'd say even taller riders have a fair amount to gain from a 65Ob conversion with very little to loose.

As far as looks go, when we start talking about frames bigger than 62cm, they will always look a bit silly and disproportionate. It ain't the bike, it's the ride.

I understand the 700c to 650b conversion but 26" to 650b isn't quite as logical. What you gain by increasing rim diameter (which isn't much) you lose in tire selection. You go from thousands of tire choices to maybe a dozen. I have an '84 Stumpjumper and I did consider swapping out the 26's for 650b's but instead I decided to buy Schwalbe's 2" (50mm) Big Apples. Got all the benefits (cushy ride, low rolling resistance, etc) for less money.

I don't think that Schwalbe 50mm Big Apples are comparable to Pari-Motos. They weigh 700-800g, depending on who you believe, versus 280g for the Pari Motos. And the Big Apple's ride is not even close to being as nice. The reason for conversion is that there are no 26" tires that are as good as the better 650b tires.

The Schwalbe Big Apple liteskin published weight is 600g and mine weighed in at 580g (yes I weighed them :)). Granted that is still almost twice as heavy but they have a reflective side wall and a side wall for a dynamo bottle. In addition, they have fantastic tread and are virtually puncture proof. The latter feature is something I highly regard for a city/commuter tire. Furthermore, I seriously question whether you'll enjoy the minuscule improvement in ride quality (if any) after you spent additional money on rims, spokes, brakes, and labor to convert from a perfectly capable 26" (and stronger) wheel. If you do think the ride is better it will only be perceived improvement to justify the unnecessary expense.

Big Apples are good rugged commuter tires, perfect if you ride through broken glass and potholes. Pari-Motos offer a ride that is an order of magnitude better; they literally transform a bike. To some the cost is a deal-killer, to others it's worthwhile.

Great info. With the new Disc Trucker, brake adjustment becomes irrelevant. For those who have done this with a 26" Trucker (either kind), what is the max 650b tire size you can run and still use fenders? Ideally I'd be looking at a 650b x 38 or so with VO hammered fenders. Will it work?

This is a good link for info about braze on distanceshttp://bikebuilding.blogspot.com/2006/12/braze-on-distances-index.htmlI don't know if it would work or not. The Zeste brakes have a lot of travel, but I'm not sure they would have enough to go from 26" to 700C

I've been working on converting a Bridgestone mb3 to a touring bike with 650b wheels. I finally got everything together and when I put the wheels in the frame I realized that the brakes pads will not line up with the rim, even at the top of their adjustment. I'm using the Tektro 720's on a rigid mtb fork, they don't line up with the front, or the rear rim. I'm pretty bummed to see this, I'd been assuming I could make this work. Any suggestions for other canti brakes I can use?Thanks.

Hey. I was the last poster here a few years ago. I'm still curious about this, I still haven't seen evidence of making canti's on a 26" bike work around a 650b rim. I tried about 4 pairs of canti's and a v brake just to be sure. And the difference is even greater when trying to convert from 700c to 650b. I dont see how y'all are pulling this off!

I know this is an old thread, but in case anyone stumbles upon it looking for answers: There are now two pretty cheap options for getting either 26" or 700C cantis studs to work for 650B. Check out Elevn Technologies brake adaptor.....its intended for BMX converions but is basically an aluminum tab the mounts onto the canti boss using the holes left when you screw out the stud. An additional pin fits into the old spring hole for extra stability. It then has an additional offset hole to screw the canti stud in. The adaptor could be mounted right side up or upside down to raise or lower the stud height by 16mm. Also check out Promax P-1 Linear V-brakes.These are cheap and have 35mm of pad adjustment. They also come in 108mm or 85mm arm length so there are options for both mtb and road levers. Hopes this helps someone trying to do a conversion.